Residua demetalation/desulfurization catalyst

ABSTRACT

A new CoMo/alumina catalyst of improved stability and activity for demetalation/desulfurization of residual oil fractions having about 40 to 75% of its pore volume in 150-200 A diameter pores and up to about 5% of its pore volume in 500 A+ diameter pores.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is concerned with an improved catalytic process for thedemetalation and desulfurization of petroleum oils, preferably thoseresidual fractions with undesirably high metals and/or sulfur contents.More particularly, the invention utilizes a demetalation-desulfurizationcatalyst characterized by novel specifications including pore sizedistribution, said catalyst comprising a Group VI B metal and an irongroup metal composited with a Delta and/or Theta phase alumina, saidcatalyst having a specific pore size distribution, and other specificcharacteristics described hereinbelow.

2. Description of the Prior Art

Residual petroleum oil fractions produced by atmospheric or vacuumdistillation of crude petroleum are characterized by relatively highmetals and sulfur content. This comes about because practically all ofthe metals present in the original crude remain in the residualfraction, and a disproportionate amount of sulfur in the original crudeoil also remains in that fraction. Principal metal contaminants arenickel and vanadium, with iron and small amounts of copper alsosometimes present. Additionally, trace amounts of zinc and sodium arefound in some feedstocks. The high metals content of the residualfractions generally preclude their effective use as charge stocks forsubsequent catalyst processing such as catalytic cracking andhydrocracking. This is so because the metal contaminants deposit on thespecial catalysts for these processes and cause the premature aging ofthe catalyst and/or formation of inordinate amounts of coke, dry gas andhydrogen.

It is current practice to upgrade certain residual fractions by apyrolytic operation known as coking. In this operation the residuum isdestructively distilled to produce distillates of low metals content andleave behind a solid coke fraction that contains most of the metals.Coking is typically carried out in a reactor or drum operated at about800° to 1100° F. temperature and a pressure of one to ten atmospheres.The economic value of the coke by-product is determined by its quality,especially its sulfur and metals content. Excessively high levels ofthese contaminants make the coke useful only as low-valued fuel. Incontrast, cokes of low metals content, for example up to about 100 ppm(parts-per-million by weight) of nickel and vanadium, and containingless than about 2 weight percent sulfur may be used in high valuedmetallurgical, electrical and mechanical applications.

Certain residual fractions are currently subjected to visbreaking, whichis a heat treatment of milder conditions than used in coking, in orderto reduce their viscosity and make them more suitable as fuels. Again,excessive sulfur content sometimes limits the value of the product.

Residual fractions are sometimes used directly as fuels. For this use, ahigh sulfur content in many cases is unacceptable for ecologicalreasons.

At present, catalytic cracking is generally done utilizing hydrocarbonchargestocks lighter than residual fractions which generally have an APIgravity less than 20. Typical cracking chargestocks are coker and/orcrude unit gas oils, vacuum tower overhead, etc., the feedstock havingan API gravity from about 15 to about 45. Since these crackingchargestocks are distillates, they do not contain significantproportions of the large molecules in which the metals are concentrated.Such cracking is commonly carried out in a reactor operated at atemperature of about 800° to 1500° F., a pressure of about 1 to 5atmospheres, and a space velocity of about 1 to 1000 WHSV.

The amount of metals present in a given hydrocarbon stream is oftenexpressed as a chargestock's "metals factor." This factor is equal tothe sum of the metals concentrations, in parts per million, of iron andvanadium plus ten times the concentration of nickel and copper in partsper million, and is expressed in equation form as follows:

    F.sub.m =Fe+V+10(Ni+Cu)

Conventionally, a chargestock having a metals factor of 2.5 or less isconsidered particularly suitable for catalytic cracking. Nonetheless,streams with a metals factor of 2.5 to 25, or even 2.5 to 50, may beused to blend with or as all of the feedstock to a catalytic cracker,since chargestocks with metals factors greater than 2.5 in somecircumstances may be used to advantage, for instance with the newerfluid cracking techniques.

In any case, the residual fractions of typical crudes will requiretreatment to reduce the metals factor. As an example, a typical Kuwaitcrude, considered of average metals content, has a metals factor ofabout 75 to about 100. As almost all of the metals are combined with theresidual fraction of a crude stock, it is clear that at least about 80%of the metals and preferably at least 90% needs to be removed to producefractions (having a metals factor of about 2.5 to 50) suitable forcracking chargestocks.

Metals and sulfur contaminants would present similar problems withregard to hydrocracking operations which are typically carried out onchargestocks even lighter than those charged to a cracking unit. Typicalhydrocracking reactor conditions consist of a temperature of 400° to1000° F. and a pressure of 100 to 3500 psig.

It is evident that there is considerable need for an efficient method toreduce the metals and/or sulfur content of petroleum oils, andparticularly of residual fractions of these oils. While the technologyto accomplish this for distillate fractions has been advancedconsiderably, attempts to apply this technology to residual fractionsgenerally fail due to very rapid deactivation of the catalyst,presumably by metals contaminants.

Hydrotreatment catalysts having specified pore distributions have beenproposed to overcome disadvantages encountered when using conventionalprior art catalysts for the hydrotreatment of petroleum residua or othermetals and sulfur-containing, heavy hydrocarbons.

Rosinski (U.S. Pat. No. 4,082,695) discloses ahydrodemetalation-desulfurization class of catalysts comprising ahydrogenating component (e.g., cobalt and molybdenum) composited with aparticular refractory base comprising theta or delta phase alumina. Thecomposite catalyst of Rosinski has a surface area of about 40-150 squaremeters per gram (m² /g) and has the following pore size distribution:not less than 60% of the total pore volume have a diameter within therange of about 100-200 Angstroms (A), not less than about 5% of thetotal pore volume are greater than 500 A in diameter. The preferredcatalyst has a surface area of 110 m² /g or less and not less than 5% ofthe total pore volume are less than about 40 A in diameter. Theefficiency of the catalyst is principally a result of the highconcentration or pores within the 100-200 A range although the largestpores (greater than about 500 A) are said to be required for conversionof exceptionally large heteroatomic molecules and the smallest pores(less than about 40 A) are thought to enhance sulfur removal generally.The distinct pore size distribution of the catalyst is believed to bedue, at least in part, to the calcination of the alumina catalyst baseduring preparation to produce a specific alumina comprising theta ordelta phase alumina.

U.S. Pat. Nos. 3,876,523; 4,016,067; and 4,054,508 disclose processesfor the demetalation and desulfurization of residua which employ theRosinski catalyst. The U.S. Pat. No. 3,876,523 discloses and claims thisuse of the catalyst generally. The U.S. Pat. No. 4,016,067 discloses adual catalyst system wherein the Rosinski catalyst is the first"demetalation" catalyst and a high surface area, smaller pore catalystis the second, "desulfurization" catalyst. The U.S. Pat. No. 4,054,508discloses a three-zone, dual catalyst process which is analogous to theU.S. Pat. No. 4,016,067 process except that there is an additional,third zone containing a relatively smaller bed of the first zonecatalyst disclosed by Rosinski.

U.S. Pat. Nos. 4,048,060 and 4,069,139 disclose an alumina-containinghydrotreating catalyst having a mean pore radius of about 70 to 95 A, atotal pore volume between 0.45 and 1.50 milliliters per gram (ml/g), atotal surface area between 130 and 500 m² /g, and the following poresize distribution: less than 0.05 ml of pore volume/g have radii greaterthan 100 A, at least 0.40 ml of pore volume/g have radii in the range ofthe mean pore radius ±10 A, at least 75% of the total pore volume haveradii in the range of the mean pore radius ±10 A, and less than 0.05 mlof pore volume/g have radii below 60 A. The method of preparing thishydrotreating catalyst and its alumina support are "conventional." U.S.Pat. No. 4,048,060 at col. 6, lines 30-36 and U.S. Pat. No. 4,069,139 atcol. 4, lines 55-60. "Conventional" alumina supports comprise gammaalumina and catalysts prepared from such supports do not have theadvantageous properties of catalysts such as those of Rosinski, supra,to which the catalysts of the present invention are related.

Other less relevant patents in this general area are: Anderson (U.S.Pat. No. 2,890,162), Erickson (U.S. Pat. No. 3,242,101), Bertolacini(U.S. Pat. No. 3,393,148), Cornelius (U.S. Pat. No. 3,669,904), Roseline(U.S. Pat. No. 3,684,688), Bertolacini (U.S. Pat. No. 3,714,032),Christman (U.S. Pat. No. 3,730,879), Wilson (U.S. Pat. No. 3,898,155),Oleck (U.S. Pat. No. 3,931,052), Hamner (U.S. Pat. No. 4,014,821), andOleck (U.S. Pat. No. 4,089,774).

SUMMARY OF THE INVENTION

It has now been found that hydrocarbon oils containing both metals andsulfur contaminants may be very effectively demetalized and desulfurizedby contact under hydrotreating conditions with hydrogen and a catalystcomprising a hydrogenation component composited with an alumina support,said composite catalyst having a particular pore size distribution. Inparticular about 40 to 75% of the total pore volume is contained inpores having a diameter within the range from about 150-200 A and up to5%, preferably from 1 to 5%, of the total pore volume is contained inpores having a diameter greater than about 500 A. The catalyst mayadditionally be characterized as having a surface area of about 90 to130 m² /g and a total pore volume of about 0.35 to 0.75 cc/g. Thecatalyst also has high-temperature delta and/or theta phases of aluminapresent.

For best results in the process of this invention, the catalyst shouldhave a total pore volume of 0.4 to 0.65 cc/g and have about 40 to 75% ofits pore volume in pores greater than 150 A up to 200 A diameter and upto about 5% of its pore volume in pores greater than 500 A diameter.

The pore volumes referred to herein, with the exception of pores lessthan 30 A diameter, are those volumes determined by mercury porosimeterusing techniques well known to those skilled in the art of catalystpreparation. Pore volume in pores less than 30 A is determined bysubtracting the pore volume accessible to mercury from the total porevolume determined independently.

Under the reaction conditions hereinafter to be described, the specifiedcatalyst exhibits improved activity and stability over known catalysts,particularly over the related Rosinski catalyst, described supra. Thepresent catalyst, which is prepared by the same general method as thatdisclosed by Rosinski (U.S. Pat. No. 4,082,695), differs therefromprimarily by a decreased macropore volume (volume of pores having adiameter greater than 500 A) and an increased concentration of 150-200 Adiameter pores.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a set of pore size distribution curves showing the pore sizedistribution of a catalyst of the present invention and those of somerelated catalysts of the type disclosed by Rosinski.

FIG. 2 is an alumina phase transformation diagram.

DETAILED DESCRIPTION OF THE INVENTION

The hydrocarbon feed to the process of this invention can be a wholecrude. However, since the high metal and sulfur components of a crudeoil tend to be concentrated in the higher boiling fractions, the presentprocess more commonly will be applied to a bottoms fraction of apetroleum oil, i.e., one which is obtained by atmospheric distillationof a crude petroleum oil to remove lower boiling materials such asnaphtha and furnace oil, or by vacuum distillation of an atmosphericresidue to remove gas oil. Typical residues to which the presentinvention is applicable will normally be substantially composed ofresidual hydrocarbons boiling above 650° F. and containing a substantialquantity of asphaltic materials. Thus, the chargestock can be one havingan initial or 5 percent boiling point somewhat below 650° F., providedthat a substantial proportion, for example, about 70 or 80 percent byvolume, of its hydrocarbon components boil above 650° F. A hydrocarbonstock having a 50 percent boiling point of about 900° F. and whichcontains asphaltic materials, 4% by weight sulfur and 51 ppm nickel andvanadium is illustrative of such chargestock. Typical process conditionsmay be defined as contacting a metal and/or sulfur contaminantcontaining chargestock with this invention's catalyst under a hydrogenpressure of about 500 to 3000 psig at 600° to 850° F. temperature, and0.1 to 5 LHSV (i.e., 0.1 to 5 volumes of chargestock per volume ofcatalyst per hour).

The hydrogen gas which is used during thehydrodemetalation-hydrodesulfurization is circulated at a rate betweenabout 1,000 and 15,000 s.c.f./bbl. of feed and preferably between about3,000 and 8,000 s.c.f/bbl. The hydrogen purity may vary from about 60 to100 percent. If the hydrogen is recycled, which is customary, it isdesirable to provide for bleeding off a portion of the recycle gas andto add makeup hydrogen in order to maintain the hydrogen purity withinthe range specified. The recycled gas is usually washed with a chemicalabsorbent for hydrogen sulfide or otherwise treated in known manner toreduce the hydrogen sulfide content thereof prior to recycling.

For the purpose of this invention, it is preferred to operate withcatalyst particles such as 1/32 inch extrudate or the equivalentdisposed in one or more fixed beds. Furthermore, the catalyst describedherein may be effectively used as the sole catalyst in the process ofthis invention. Alternatively, a dual bed arrangement such as describedin U.S. Pat. No. 4,016,067 issued Apr. 5, 1977, or a dual catalyst,three bed arrangement such as described in U.S. Pat. No. 4,054,508issued Oct. 18, 1977, may be used. The entirety of both of these patentsis incorporated into this specification by reference. The catalyst ofthis invention may advantageously be substituted for the "1st catalyst"disclosed in the U.S. Pat. No. 4,016,067 and for the catalyst of the 1stand 3rd zones of the U.S. Pat. No. 4,054,508. The catalyst may bepresulfided, if desired, by any of the techniques known to those skilledin the art.

The hydrogenating component of the class of catalysts disclosed hereincan be any material or combination thereof that is effective tohydrogenate and desulfurize the chargestock under the reactionconditions utilized. For example, the hydrogenating component can be atleast one member of the group consisting of Group VI and Group VIIImetals in a form capable of promoting hydrogenation reaction, especiallyeffective catalysts for the purposes of this invention are thosecomprising molybdenum and at least one member of the iron group metals.Preferred catalysts of this class are those containing about 2 to about10 percent by weight cobalt and about 5 to about 20 percent by weightmolybdenum, but other combinations of iron group metals and molybdenumsuch as iron, nickel and molybdenum, as well as combinations of nickeland molybdenum, cobalt and molybdenum, nickel and tungsten or otherGroup VI or Group VIII metals of the Periodic Table taken singly or incombination. The hydrogenating components of the catalysts of thisinvention can be employed in sulfided or unsulfided form.

When the use of a catalyst in sulfided form is desired, the catalyst canbe presulfided, after calcination, or calcination and reduction, priorto contact with the chargestock, by contact with a sulfiding mixture ofhydrogen and hydrogen sulfide, at a temperature in the range of about400° and 800° F., at atmospheric or elevated pressures. Presulfiding canbe conveniently effected at the beginning of an onstream period at thesame conditions to be employed at the start of such period. The exactproportions of hydrogen and hydrogen sulfide are not critical, andmixtures containing low or high proportions of hydrogen sulfide can beused. Relatively low proportions are preferred for economic reasons.When the unused hydrogen and hydrogen sulfide utilized in thepresulfiding operation is recycled through the catalyst bed, any waterformed during presulfiding is preferably removed prior to recyclingthrough the catalyst bed. It will be understood that elemental sulfur orsulfur compounds, e.g., mercaptans, or carbon desulfide that are capableof yielding hydrogen sulfide at the sulfiding conditions, can be used inlieu of hydrogen sulfide.

Although presulfiding of the catalyst is preferred, it is emphasizedthat this is not essential as the catalyst will normally become sulfidedin a very short time by contact, at the process conditions disclosedherein, with the high sulfur content feedstocks to be used.

When compared with prior art catalysts such as those of U.S. Pat. Nos.4,069,139 and 4,048,060, the uniqueness of the catalyst of thisinvention is believed to be due to the fact that the alumina basecatalyst is calcined to a particular temperature, thereby producing aspecific alumina comprising theta or delta phase alumina. These phasesare believed to produce the distinct pore size distribution of thecatalyst. When compared with the catalysts disclosed by U.S. Pat. No.4,082,695, the uniqueness of the catalyst of this invention is due tothe higher concentration of pores in the 150-200 A diameter range andthe lower concentration of pores in the 500 A+ diameter range. Table Ibelow shows a comparison of the properties of catalyst of this invention(Catalyst C) with the properties of catalysts disclosed in the U.S. Pat.No. 4,082,695 (Catalysts A and B).

                  TABLE I                                                         ______________________________________                                        Properties of Resid                                                           Hydroprocessing Catalysts                                                                     Catalysts                                                                     A      B        C                                             ______________________________________                                        Chemical Composition, Wt. Pct.                                                Cobaltous Oxide   3.4      3.3      3.7                                       Molybdena         10.6     9.9      9.6                                       Alumina           Balance  Balance  Balance                                   Physical Properties                                                           Surface Area, Sq. M/G                                                                           104      112      112                                       Real Density, G/CC                                                                              3.64     3.44     3.69                                      Particle Density, G/CC                                                                          1.31     1.25     1.27                                      Pore Volume, CC/G 0.490    0.509    0.516                                     Pore Size Distribution, CC/G                                                  0/30   Angstroms      0.056    0.053  0.030                                   30/50  "              0.006    0.006  0.008                                   50/80  "              0.007    0.012  0.012                                   80/100 "              0.017    0.049  0.029                                   100/150                                                                              "              0.139    0.177  0.116                                   150/200                                                                              "              0.176    0.137  0.281                                   200/300                                                                              "              0.047    0.008  0.010                                   300/500                                                                              "              0.002    0.003  0.008                                   500+   "              0.040    0.064  0.022                                   ______________________________________                                    

The unique pore size distribution of the catalyst of this invention isfurther graphically illustrated by FIG. 1. A particular method ofpreparing this catalyst is explained in detail in Example 17.

As noted in Alumina Properties, p. 46 by Newsome, Heiser, Russel andStumpf (Alcoa Research Laboratories 1960), the theta alumina phase mayonly be reached through employing an alpha monohydrate or a betatrihydrate alumina form. Calcining temperatures required to achieve thetheta phase vary depending on which alumina form is utilized as theinitial alumina. An alpha monohydrate enters the gamma phase at about500° C., crosses the transition point into the delta phase at about 860°C. and enters the narrowly temperature banded theta phase at about 1060°C. The transition point between theta and alpha phases being at about1150° C.

When utilizing a beta trihydrate as an initial alumina, the theta phaseis broader, its limits being about 860° to about 1160° C. It should benoted that both beta trihydrate and alpha trihydrate aluminas may alsobe transformed into the alpha monohydrate form. Thus, either the alphamonohydrate or the beta trihydrate aluminas are suitably calcined to atemperature of about 1700°-2000° F. for the purposes of this invention.The alumina phase diagram is presented in FIG. 2.

EXAMPLES 1-4

Comparative runs were conducted using fresh (less than five days onstream) B and C catalysts. The characteristics of these catalysts areshown in Table 1 and their pore size distributions are shown in FIG. 1.An atmospheric residual oil from Light Arabian crude containing about 3%sulfur and about 33 ppm of vanadium and nickel was the charge. Otheroperating conditions and results are shown in Table II below. Includedin Table II are catalyst performances for heteroatom removal and CCr(Conradson Carbon Residue) reduction corrected to 0.5 LHSV. The modifiedcatalyst of Examples 3 and 4 (Catalyst C, a catalyst of this invention)was consistently higher in both desulfurization and demetalation. Acomparison of the 5-day aged catalyst properties indicates that CatalystC maintained a slightly higher pore volume and surface area.

                                      TABLE II                                    __________________________________________________________________________    Fresh Activity for Catalysts B and C                                          Charge:Arab Lt Atmospheric Resid                                              Example          1    2        3    4                                         Catalyst     --  B    B    --  C    C                                         __________________________________________________________________________    Balance Conditions                                                            Temperature, °F.                                                                    --  672  720  --  674  723                                       Pressure, psig                                                                             --  2000 2000 --  2000 2000                                      LHSV, CC CHG/CC                                                               CAT-HR       --  0.52 0.54 --  0.49 0.49                                      Days on Stream                                                                             --  3.4  4.4  --  3.5  4.5                                       H2 Circulation                                                                SCF/B        --  6410 6316 --  6214 6310                                      Yields                                                                        C5+,Wt.Pct   100.00                                                                            98.56                                                                              97.92                                                                              100.00                                                                            98.78                                                                              98.04                                     1000° F.+, Vol                                                         Pct          32.14                                                                             28.91                                                                              26.53                                                                              33.97                                                                             29.33                                                                              24.94                                     H2 Consump-                                                                   tion, SCF/B  --  412  661  --  549  644                                       TLP Properties                                                                H, Wt Pct    11.72                                                                             12.40                                                                              12.71                                                                              11.63                                                                             12.53                                                                              12.67                                     Gravity, °API                                                                       19.6                                                                              23.6 25.4 19.2                                                                              23.4 25.3                                      S, Wt Pct    2.91                                                                              1.16 0.60 2.79                                                                              0.85 0.47                                      N, Wt Pct    0.15                                                                              0.14 0.11 0.15                                                                              0.15 0.17                                      CCR, Wt Pct  6.48                                                                              4.61 2.96 7.17                                                                              4.05 3.05                                      V, PPM       27.0                                                                              2.4  0.5  28.9                                                                              2.3  0.1                                       Ni, PPM      5.4 1.9  0.8  4.4 1.2  0.4                                       Catalyst Performance                                                          Corrected to 0.5 LHSV                                                         PCT Demetalation                                                                           --  87.5 96.6 --  89.3 98.5                                      PCT Desulfuriza-                                                              tion         --  61.3 80.6 --  69.7 83.4                                      PCT Denitrogen-                                                               ation        --  8.2  29.2 --  1.9  --                                        PCT CCR Removal                                                                            --  30.5 57.1 --  43.9 58.0                                      Aged Catalyst Properties                                                      Pore Volume, CC/G                                                                          --  --   0.380                                                                              --  --   0.393                                     Surface Area,                                                                 Sq. M/G      --  --   104  --  --   108                                       Coke, G/100G                                                                  Fresh        --  --   13.6 --  --   12.3                                      V, G/100G Fresh                                                                            --  --   0.02 --  --   0.02                                      Ni, G/100G Fresh                                                                           --  --   0.05 --  --   0.08                                      __________________________________________________________________________

EXAMPLES 5-8

A similar set of experiments was carried out using a vacuum residual oilfrom Light Arabian crude containing about 4% sulfur and 85 ppm metals(V+Ni). Results and operating conditions are summarized in Table III.Again, the modified catalyst of Examples 7-8 was more active fordesulfurization and demetalation. The decreased coke deposition onCatalyst C (14.5 wt. % on Catalyst C vs. 16.9 wt. % on Catalyst B) isprobably responsible for the improved activity of this catalyst.

                  TABLE III                                                       ______________________________________                                        Fresh Activity for Catalysts B and C                                          Charge:Arab Lt Vacuum Resid(75D2500 Series)                                   Example                  5      6    7    8                                   Catalyst         --      B      B    C    C                                   ______________________________________                                        Balance Conditions                                                            Temperature, °F.                                                                        --      674    725  674  724                                 Pressure, PSIG   --      2000   2000 2000 2000                                LHSV, CC CHG/CC Cat-HR                                                                         --      0.47   0.50 0.52 0.50                                Days on Stream   --      4.0    5.0  4.0  5.0                                 H2 Circulation, SCF/B                                                                          --      5000   5000 3691 4473                                Yields                                                                        C5+, Wt Pct      100.00  98.85  98.01                                                                              98.28                                                                              97.08                               1000 °F.+, Vol Pct                                                                      86.06   80.69  76.75                                                                              78.34                                                                              75.78                               H2 Consumption, SCF/B                                                                          --      188    441  355  561                                 TLP Properties                                                                H, Wt Pct        10.62   10.90  11.28                                                                              11.20                                                                              11.49                               Gravity, °API                                                                           8.3     11.2   12.1 12.3 14.3                                S, Wt Pct        4.23    2.82   1.90 2.19 1.28                                N, Wt Pct        0.28    0.27   0.25 0.27 0.25                                CCR, Wt Pct      17.00   13.37  11.32                                                                              12.92                                                                              10.83                               V, PPM           68.0    31.0   17.5 28.1 11.0                                Ni, PPM          17.0    12.0   7.9  11.1 5.1                                 Catalyst Performance                                                          Corrected to 0.5 LHSV                                                         Pct Demetalation --      49.0   70.6 55.5 81.5                                Pct Desulfurization                                                                            --      33.6   56.0 49.7 70.5                                Pct Denitrogenation                                                                            --      4.9    12.7 3.6  13.3                                Pct CCR Removal  --      21.9   34.8 25.8 38.2                                Aged Catalyst Properties                                                      Pore Volume, CC/G                                                                              --      --     0.442                                                                              --   0.406                               Surface Area, Sq. M/G                                                                          --      --     110  --   104                                 Coke, G/100G Fresh                                                                             --      --     16.9 --   14.5                                V, G/100G Fresh  --      --     0.40 --   0.36                                Ni, G/100G Fresh --      --     0.04 --   0.10                                ______________________________________                                    

EXAMPLES 9-16

A comparative evaluation of aged Catalysts B and C using a vacuumresidual oil from Light Arabian crude is shown in Tables IV and V. Priorto the runs shown, the subject catalysts were aged in a multi-catalystbasket reactor at 750° F., 2000 psig, 5000 standard cubic feed ofhydrogen per barrel of charge, and 0.5 LHSV with the same charge stock.The modified catalyst of Examples 13-16, Catalyst C, retained itsactivity advantage over Catalyst B. Note that 20% less coke was formedon the modified catalyst while it effected greater reduction of theConradson Carbon Residue of the charge. Although the higher activitycatalyst is more efficient at removing heteroatoms from the asphaltenes(pentane-soluble material), there was little difference in activity forthe conversion of asphaltenes. Another important improvement in theactivity observed for the modified catalyst is a 5% advantage inmolecular weight reduction. This reduction can aid in any downstreamcatalytic process in which the reaction is diffusion limited includingsecond-stage hydrotreating. Again, decreased coke deposition wasobserved in the modified catalyst. This may be attributable to thedecreased macropore (500 A+ diameter) volume of Catalyst C andconsequent greater diffusional restriction exhibit thereby.

                  TABLE IV                                                        ______________________________________                                        Activity for Aged (20 Days;750° F.;0.5 LHSV)                           Catalyst B                                                                    Charge:Arab Lt Vacuum Resid                                                   Example                  9      10   11   12                                  Catalyst         --      B      B    B    B                                   ______________________________________                                        Balance Conditions                                                            Temperature, °F.                                                                        --      673    722  725  774                                 Pressure, PSIG   --      2000   2000 2000 2000                                LHSV, CC CHG/CC  --      0.38   0.47 0.50 0.58                                CAT-HR                                                                        Days on Stream   --      1.3    1.9  2.3  3.5                                 H2 Circulation, SCF/B                                                                          --      6669   4133 5737 4753                                Yields                                                                        C5+, Wt Pct      100.00  99.15  98.32                                                                              97.79                                                                              96.31                               1000°  F.+, VOL PCT                                                                     86.06   81.27  75.69                                                                              77.97                                                                              62.01                               H2 Consumption, SCF/B                                                                          --      229    186  217  467                                 TLP Properties                                                                H, Wt Pct        10.62   10.94  10.89                                                                              10.90                                                                              11.17                               Gravity, °API                                                                           8.3     11.3   10.0 12.2 15.8                                S, Wt Pct        4.23    3.07   2.79 2.59 1.95                                N, Wt Pct        0.28    0.28   0.27 0.25 0.24                                CCR, Wt Pct      17.00   12.66  13.77                                                                              13.54                                                                              11.50                               V, PPM           68.0    35.0   29.0 23.0 9.2                                 Ni, PPM          17.0    12.0   11.0 9.9  6.1                                 Mol. Wt.         813     724    702  730  585                                 Asphaltenes, Wt Pct                                                                            15.65   8.89   --   8.04 6.71                                Catalyst Performance                                                          Corrected To 0.5 LHSV                                                         Pct Demetalation --      39.6   52.2 62.3 85.5                                Pct Desulfurization                                                                            --      24.6   34.2 40.2 58.1                                Pct Denitrogenation                                                                            --      --     5.0  12.7 19.0                                Pct CCR Removal  --      22.4   19.6 22.7 37.9                                Mol. Wt.         818     747    709  730  548                                 Pct Asph. Conversion                                                                           --      38.2   --   49.9 62.5                                Aged Catalyst Properties                                                      Pore Volume, CC/G                                                                              --      --     --   --   0.381                               Surface Area, Sq. M/G                                                                          --      --     --   --   99                                  Coke, G/100G Fresh                                                                             --      --     --   --   15.7                                V, G/100G Fresh  --      --     --   --   2.37                                Ni, G/100G Fresh --      --     --   --   0.42                                ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        Activity for Aged (20 Days;750° F.;0.5 LHSV)                           Catalyst C                                                                    Charge:Arab Lt Vacuum Resid                                                   Example                  13     14   15   16                                  Catalyst         --      C      C    C    C                                   ______________________________________                                        Balance Conditions                                                            Temperature, °F.                                                                        --      675    725  726  774                                 Pressure, PSIG   --      2000   2000 2000 2000                                LHSV, CC CHG/CC  --      0.49   0.43 0.44 0.45                                CAT-HR                                                                        Days on Stream   --      1.1    1.6  2.1  3.1                                 H2 Circulation, SCF/B                                                                          --      5355   6143 5730 5475                                Yields                                                                        C5+, Wt Pct      100.00  98.90  97.65                                                                              97.96                                                                              95.79                               1000°  F.+, Vol Pct                                                                     86.06   80.11  76.67                                                                              75.96                                                                              56.34                               H2 Consumption, SCF/B                                                                          --      427    294  435  690                                 TLP Properties                                                                H, Wt Pct        10.62   11.23  11.06                                                                              11.24                                                                              11.49                               Gravity, °API                                                                           8.3     12.1   13.3 13.1 17.0                                S, Wt Pct        4.23    2.85   2.16 2.29 1.39                                N, Wt Pct        0.28    0.27   0.26 0.26 0.23                                CCR, Wt Pct      17.00   13.22  12.18                                                                              12.64                                                                              10.16                               V, PPM           68.0    37.0   15.0 18.0 3.8                                 Ni, PPM          17.0    12.0   7.9  8.3  4.0                                 Mol. Wt.         813     723    649  647  497                                 Asphaltenes, Wt Pct                                                                            15.65   9.05   --   8.32 6.18                                Catalyst Performance                                                          Corrected to 0.5 LHSV                                                         Pct Demetalation --      42.4   70.0 66.4 89.8                                Pct Desulfurization                                                                            --      32.9   47.5 44.7 67.0                                Pct Denitrogenation                                                                            --      4.5    8.5  8.3  20.2                                Pct CCR Removal  --      22.7   27.5 25.1 40.6                                Mol. Wt.         --      725    673  668  529                                 Pct Asph. Conversion                                                                           --      42.2   --   44.9 60.3                                Aged Catalyst Properties                                                      Pore Volume, CC/G                                                                              --      --     --   --   0.359                               Surface Area, Sq. M/G                                                                          --      --     --   --   97                                  Coke, G/100G Fresh                                                                             --      --     --   --   12.3                                V, G/100G Fresh  --      --     --   --   2.42                                Ni, G/100G Fresh --      --     --   --   0.43                                ______________________________________                                    

EXAMPLE 17

A preparation procedure for the demetalation-desulfurization class ofcatalysts of this invention may be defined as follows:

About 7000 grams of Catapal SB commercial alumina powder weremixed-mulled with about 4300 ml water and auger extruded to 1/32 inchdiameter cyclinders. These were dried at 250° F., calcined in flowingair 10 hours at 1000° F. and then in stagnant atmosphere for 4 hours at1700° F. to transform the alumina to the desired characteristics.

About 700 grams of the calcined extrudate were impregnated to incipientwetness with 427 ml of a solution containing 98.1 gms ammoniumheptamolybdate (81.5%/MoO₃); and dried overnight in an oven at 250° F.

The dried material was impregnated to incipient wetness with 281 ml of asolution containing 110.0 grams of cobaltous nitrate hexahydrate anddried at 250° F. overnight. Finally, the cobalt-molybdenum impregnatedalumina was calcined to about 1000° F. at a gradually increasingtemperature of about 5° F./min. and held at 1000° F. for about 6 hours.

In summary of the preferred embodiments, this invention provides ahydrodemetalation-desulfurization catalyst comprising a hydrogenatingcomponent selected from the group of oxides or sulfides of at least oneGroup VIB or Group VIII metal composited with an alumina base whichcomprises theta or delta phase alumina and which composite has a surfacearea of 40-150 m² /g, a pore volume of 0.45-1.50 cc/g, and has not lessthan about 60% of its pore volume in pores with diameters of about 100 Ato about 200 A; with an improvement which comprises providing acomposite having about 40 to 75% of its pore volume in pores withdiameters of about 150 A to about 200 A and up to about 5% of its porevolume in pores with diameters greater than about 500 A.

In another embodiment, the catalyst composite has from 1 to 5% of itspore volume in pores with diameters greater than about 500 A.

In another embodiment, the catalyst hydrogenating component consistsessentially of about 2 to about 10 wt.% cobalt and about 5 to about 20wt.% molybdenum.

In another embodiment, the catalyst alumina base is produced bycalcining an alpha monohydrate to a temperature of about 1600-2000° F.

In a further embodiment, the catalyst composite has a surface areawithin the range of about 90 to 130 m² /g and a pore volume within therange of about 0.45 to 0.65 cc/g.

What is claimed is:
 1. In a hydrodemetalation-desulfurization catalystcomprising a hydrogenating component selected from the group of oxidesor sulfides of at least one Group VI B or Group VIII metal compositedwith an alumina base which comprises theta and/or delta phase aluminaand which composite has a surface area of 40-150 m² /g, a pore volume of0.45-1.50 cc/g, and has not less than about 60% of its pore volume inpores with diameters of about 100 A to about 200 A; wherein saidhydrogenating component consists essentially of about 2 to about 10 wt.%cobalt and about 5 to about 20 wt.% molybdenum; the improvement whichcomprises providing a composite having about 40 to 75% of its porevolume in pores with diameters of about 150 A to about 200 A and up toabout 5% of its pore volume in pores with diameters greater than about500 A.
 2. The catalyst of claim 1 wherein said alumina base is producedby calcining an alpha monohydrate to a temperature of about 1600-2000°F.